What should be the characteristic of ground rods used in lightning protection?

Ground rods used in lightning protection systems are critical in providing a safe path for lightning energy to dissipate into the earth. The correct choice emphasizes the importance of having a low resistance to ground. This characteristic ensures that when lightning strikes, the energy can flow easily through the ground rod and into the earth, minimizing the risk of damage to structures and electrical systems.

A low resistance to ground improves the effectiveness of the grounding system. Ideally, the resistance should be as low as possible, typically below 25 ohms, allowing for a more efficient dissipation of electrical energy. This is crucial because high resistance can lead to dangerous voltage levels and ineffective grounding, which can cause equipment malfunction or even fire hazards.

In contrast, the other options do not support the necessary characteristics of a ground rod in lightning protection systems. For instance, using plastic for ground rods undermines their ability to conduct electricity effectively. Insulation would prevent the ground rod from performing its purpose, as it must make direct contact with the earth. Additionally, while driving ground rods deeper can improve grounding in certain situations, there is no absolute depth requirement like 10 feet; rather, achieving low resistance is the priority regardless of the depth.

Focusing on low resistance ensures the ground rod serves its intended